Spatiotemporal analysis of temperature trends under climate change in the source region of the Yellow River, China

Under global climate change, the change in temperature has greatly affected the hydrological processes and water resource security in the source region of the Yellow River, which is located in the Qinghai-Tibet Plateau and serves as a major source of domestic and agricultural water supply in the watershed. Multiple spatiotemporal analysis methods, including the S-mode empirical orthogonal function analysis, the inverse distance weighted interpolation, the weighted moving average method, and the Mann-Kendall test method were used to comprehensively analyze the temperatures of 14 meteorological stations at yearly and seasonal scales from 1961 to 2010. The results indicated that (1) general trends of temperature change have been rising, with an especially significant warming trend since the late 1990s; (2) in the last five decades, temperature trends in the study area underwent three stages, namely a cool stage (approximately 1961-1980), a fluctuating stage (approximately 1981-1997), and a warm stage (approximately 1998-2010); and (3) due to the combined effects of monsoons and geographic features, the source region could be divided into three zones according to the annual temperature variations: a low-value zone centered on Henan station in the northeastern edge; a high-value zone situated in the central, southern, and western area; and a transitional zone between the two zones mentioned above. This study is helpful for understanding temperature trends under climate change and can provide a basis for ecological protection.